Process for producing sintering feedstock and apparatus therefor

ABSTRACT

As a pretreatment of a manufacturing process of sintered ore, a sintering material including iron ore, a SiO 2 -containing material, a limestone base powdery material and a solid fuel type powdery material is projected as a additional coating auxiliary raw material into the drum mixer with a additional coating conveyor disposed in proximity to an exhaust outlet of the drum mixer. Preferably, a sintering material excepting a limestone base powdery material and a solid fuel type powdery material is charged from a charge inlet of the drum mixer to granulate and in a region disposed on a downstream side, an additional coating auxiliary raw material including a limestone base powdery material and a solid fuel type powdery material is added, and thereby until reaching the exhaust outlet, the additional coating auxiliary raw material is deposited and formed on a exterior coating portion of the sintering material.

TECHNICAL FIELD

The present invention relates to a manufacturing method of a materialfor sintering that is used when sintered ores for a blast furnace aremanufactured by use of a Dwight-Lloyd type sintering machine of downwardsuction system, and a manufacturing apparatus thereof.

BACKGROUND ART

Sintered ores that are used as a material for blast furnaces aregenerally manufactured by undergoing a treatment process of a sinteringmaterial as shown below. As shown in FIG. 1, at first, iron ores M1 witha particle size of 10 mm or less, an SiO₂-containing material M2including silica rock, serpentine rock or nickel slag, a CaO-containinglimestone base powdery material M3 such as limestone, and a solid fueltype powdery material M4 that is a heat source such as powdery coke oranthracite are mixed together with an appropriate amount of waterfollowed by granulating by means of a drum mixer 4, and therebygranulated products called as pseudo-particles are formed.

The blended material including the granulated products is charged on apallet of a Dwight-Lloyd sintering machine with an appropriate thicknessof, for instance, 500 to 700 mm, a solid fuel at a surface thereof isignited, after the ignition, the solid fuel is combusted with airsucking downwardly, and, by the combustion heat, the blended sinteringmaterial is sintered to be a sintered cake. The sintered cake ispulverized and screened, and thereby sintered ores having a particlesize larger than a predetermined diameter are obtained. On the otherhand, ores having a particle size smaller than the predetermineddiameter are returned and used again as the sintering material.

The reducibility of the sintered ore product thus manufactured is, as sofar pointed out, a factor that largely controls an operationparticularly of the blast furnace. Ordinarily, the reducibility of thesintered ores is defined according to JIS M8713 (JIS: JapaneseIndustrial Standard, hereinafter referred to as JIS), and here thereducibility of the sintered ores is denoted with JIS-RI.

As shown in FIG. 2, there is a positive correlation between thereducibility (JIS-RI) of the sintered ores and a gas utilization factor(η_(co)) in the blast furnace, and furthermore, as shown in FIG. 3,there is a negative correlation between the gas utilization factor(η_(co)) in the blast furnace and a fuel ratio. Accordingly, thereducibility (JIS-RI) of the sintered ores is in an excellent negativecorrelation with the fuel ratio through the gas utilization factor(η_(co)) in the blast furnace. As a result, when the reducibility of thesintered ores is improved, the fuel ratio in the blast furnacedecreases.

The gas utilization factor (η_(co)) and the fuel ratio are defined asfollows.Gas utilization factor (η_(co))=CO₂ (%)/(CO (%)+CO₂ (%))

Here, CO₂ (%) and CO (%) each mean volume % in a furnace top gas of theblast furnace.Fuel ratio=(amount of coal+coke used (kg))/amount of pig (1 ton)

Furthermore, the cold strength of the sintered ore product thusmanufactured is also an important factor for securing the ventilation inthe blast furnace. In the individual blast furnaces, the lower limit ofthe cold strength is set and operated. Accordingly, the sintered orespreferable for the blast furnace are one that is excellent in thereducibility and high in the cold strength. In Table 1, the reducibilityand the tensile strength of four main ore textures that constitute thesintered ores, that is, calcium ferrite (CF): nCaO.Fe₂O₃, hematite (He):Fe₂O₃, calcium silicate containing FeO (CS): CaO.xFeO. ySiO₂, andmagnetite (Mg): Fe₃O₄ are shown. As shown in Table 1, one that is highin the reducibility is hematite (He) and one that is high in the tensilestrength is calcium ferrite (CF).

The desired sintered ore structure that the invention intends is, asshown in FIG. 4, one that has calcium ferrite (CF) high in the strengthgenerated on a surface of the sintered ore and has hematite (He) high inthe reducibility selectively generated toward the inside of the sinteredore. Calcium silicate (CS) low in the reducibility and the strengthshould not be formed as far as possible.

However, so far, as mentioned above, the iron ore M1, SiO₂-containingmaterial M2, limestone base powdery material M3 and solid fuel typepowdery material M4 are simultaneously mixed and granulated.Accordingly, as shown in FIG. 5, in the pseudo particle structure, thereare powdery ores, lime, and coke mixed in the surroundings of coarseseed ores. Accordingly, in the sintered ore structure obtained by thesintering, four ore textures of hematite (He), calcium ferrite (CF),calcium silicate (CS) and magnetite (Mg) are mingled.

In this connection, so far, various methods have been tried so as toproduce much calcium ferrite (CF) and hematite (He). For instance,calcium silicate (CS) is produced a lot when the sintering is carriedout at high temperatures. Accordingly, in Japanese Unexamined PatntApplication Publication No. 63-149331, a technology is proposed in whichpowdery iron ore, together with a binder and limestone, is granulatedfollowed by coating powdery coke that is a heat source on a surface toimprove the combustibility of coke, this is sintered at low temperaturesand thereby the reducibility is improved.

However, according to the conventional method proposed in JapaneseUnexamined Patnt Application Publication No. 63-149331, since CaO andSiO₂ in the iron base material or SiO₂ base material are in proximity toeach other, calcium silicate (CS) is inevitably produced much.Accordingly, in many cases, a structure mainly including calcium ferrite(CF) and hematite (He) is not necessarily obtained.

Furthermore, Japanese Unexamined Patnt Application Publication No.63-69926 proposes a technology in which after powdery iron ore and/orreturned ore is mixed, to the mixed powdery iron ore and/or returned orelimestone, powdery coke and auxiliary raw materials such as scale andsilica rock are added to form pseudo particles, thereby the powdery cokecan be deposited much on an outer periphery portion of the pseudoparticle, thereby the combustion speed of the powdery coke isaccelerated, resulting in shortening the combustion time.

However, according to the conventional method proposed in JapaneseUnexamined Patnt Application Publication No. 63-69926, since limestoneand silica rock in the auxiliary raw materials are present together,calcium silicate (CS) weakest in the tensile strength is produced a lot,resulting in fragile sintered ores low in the strength.

Still furthermore, Japanese Unexamined Patnt Application Publication No.11-241124 discloses a method of manufacturing low SiO₂ sintered ores inwhich, after iron ore powder, returned ores, part or whole of calcinedlime and limestone and part or whole of SiO₂ source material are mixedand granulated by use of a primary mixer, powdery coke divided fromanother system and the slug source such as silica rock and lime areadded to the mixed and granulated material followed by granulating byuse of a secondary mixer, thereby on a surface portion of the granulatedparticle a layer of powdery coke and slug source is formed, and thusobtained material is sintered to obtain the low SiO₂ sintered ores.

However, according to the technology disclosed in Japanese UnexaminedPatnt Application Publication No. 11-241124, in an exterior coatingportion of the granulated particle (that is, one corresponding to apseudo-particle of the invention), the low SiO₂-containing material islikely to enter. Thereby, calcium silicate (CS) lowest in the tensilestrength among constituent ores of the sintered ore as shown in Table 1is formed, resulting in lowering the Chatter Index or the Tumbler Indexthat denotes the cold strength. Furthermore, inside of the granulatedparticle, the material partially containing limestone enters;accordingly inside of the sintered ore, not only hematite (He) high inthe reducibility but also calcium ferrite (CF) inferior in thereducibility to hematite (He) and calcium silicate (CS) much inferior inthe reducibility to the hematite (He) are formed; as a result, adramatic improvement effect in the reducibility cannot be obtained.

Furthermore, Japanese Unexamined Patnt Application Publication No.61-163220 discloses a pre-treatment method of the sintering material. Inthe method, a sintering material, in which, pellet is mixed while thehumidity therein is controlled, is mixed by use of a primary mixer andsubsequently, powdery coke is added to the humidity-controlled andgranulated substance which is then subjected to rollintg granulation byuse of a secondary mixer.

However, according to the technology disclosed in Japanese UnexaminedPatnt Application Publication No. 61-163220, since the materialcontaining limestone enters inside of the pseudo particles, inside ofthe sintered ores, not only hematite (He) high in the reducibility butalso calcium ferrite (CF) inferior in the reducibility to hematite (He)and calcium silicate (CS) remarkably inferior in the reducibility to thehematite (He) are formed. Accordingly, not only the dramatic improvementeffect of the reducibility cannot be obtained, but also in the outsideof the sintered ore where the cold strength has to be secured, calciumsilicate (CS) lowest in the tensile strength among the ingredient oresof the sintered ore is formed, resulting in decreasing in the ChatterIndex or the Tumbler Index that denotes the cold strength.

As disclosed in Japanese Unexamined Patnt Application PublicationNos.61-163220, 63-69926 and 11-241124, in the pre-treatment method ormanufacturing method of the sintering material in which with the primaryand secondary mixers, the mixing and granulation are carried out,fundamentally the primary mixer performs the mixing and granulationmainly consisting of the mixing of the sintering material, andthereafter, the secondary mixer carries out the granulation. When thereare the primary and secondary mixers like this (when there are twomixers in total), ordinarily, for the mixing and granulation of thesintering material in the primary mixer, substantially 120 seconds aresecured, and for the granulation in the secondary mixer, substantially180 seconds are secured.

Furthermore, as to the additional coating of powdery coke and limestone,in Japanese Unexamined Patnt Application Publication No.2002-285250, anapplicant the same as the present invention discloses a manufacturingmethod of a sintering material that the present invention intends toobtain. That is, there is proposed a granulation method in which byadditionally coating powdery coke and limestone, so-called three-layerpseudo particles are obtained. The additional coating of powdery cokeand limestone intends to deposit an auxiliary raw material including theadditionally coated powdery coke and limestone on a surface of thepseudo particle. Thereby, to the pseudo particle with a first layer of acoarse particle and a second layer of fine particles surrounding thecoarse particle, on a surface layer of the pseudo particle a third layerrich in powdery coke and limestone is formed, and thereby thereducibility JIS-RI value of the sintered ore can be improved.

However, even in the Japanese Unexamined Patnt Application PublicationNo. 2002-285250, it was found that when powdery coke and limestone wereadditionally coated in the course of granulation, in the drum mixer,other than an action of forming the pseudo particles owing to rolling ofthe drum mixer, breaking down of the pseudo particles was repeated inthe course of the rolling; in this breaking down process, powdery cokeand limestone were contained inside of the pseudo particles; as aresult, powdery coke and limestone could not be coated on the surface ofthe pseudo particles.

Furthermore, in Japanese Unexamined Patnt Application Publication No.2002-285250, powdery coke and limestone are additionally coated byinserting a belt conveyer into a drum mixer to add.

However, the aditional coating method described in Japanese UnexaminedPatnt Application Publication No. 2002-285250, in particular a methodthat uses a belt conveyer has the following disadvantages. That is,deposit adhered to an inner wall of the drum mixer in the course of thegranulation of the material for sintering falls down on the beltconveyer to adhere to and deposit on the belt conveyer. In order toremove the accretion and deposit, it takes a lot of labor. Furthermore,in some cases, a driving part of the belt conveyer is damaged and anoperation is interrupted. Still furthermore, when the accretion on thebelt conveyer becomes too large, the accretion comes into contact withthe inner wall of the drum mixer, or the belt conveyer is bent owing toa weight of the accretion to come into contact with the inner wall ofthe drum mixer. It was found that such a contact of the inner wall ofthe drum mixer and the accretion gave rise to a large damage onto theinner wall of the drum mixer, other than the interruption of theoperation was caused, there was a large problem also from the viewpointof safety.

Furthermore, Japanese Unexamined Patnt Application Publication No.58-189335 discloses another additional coating method. According to themethod, over a region from an intermediate portion in a direction inwhich material in the drum mixer flows to an ore exhaust side (exhaustside), an air stream is used to inject and add from the exhaust side.

However, according to the method disclosed in Japanese Unexamined PatntApplication Publication No. 58-189335, equipment expense for an airstream generator that additionally coats auxiliary raw materials,apparatus for transferring additional coating additives and injectionequipment becomes enormous. Furthermore, to a portion that is inside ofthe drum mixer of the injection equipment, the accretion falls from theinner wall of the drum mixer or dust powder adheres to apparatusportion, resulting in disturbing a smooth operation. Furthermore,according to the method, since the additional coating material isinjected and added toward a charge side of the drum mixer by the airstream, the additional coating material is widely scattered within thedrum mixer and reaches to the charge side of the drum mixer. As aresult, a problem is caused in that since such auxiliary raw materialthat were scattered up to the charge side are contained in the sinteringmaterial in the course of granulation in the drum mixer, the intentionof depositing the additional coating auxiliary raw material on thepseudo particle surface cannot be realized.

Still furthermore, a still another additional coating method is proposedin Japanese Unexamined Patnt Application Publication No. 2002-20820.According to the method, in a predetermined region on a sinteringmaterial charge side in the drum mixer, by making use of an air stream,a binder consisting limestone powder and hydrated lime and so on isdispersed and added.

However, even according to the method disclosed in Japanese UnexaminedPatnt Application Publication No. 2002-20820, since a portion of theapparatus that projects the additional coating auxiliary raw material isalways inside of the drum mixer, dust powder (calcined lime and so on)in the drum mixer adheres and solidly sticks to the portion of theapparatus and disturbs the operation. Accordingly, the maintenanceoperation that periodically interrupts the operation and pulls theportion of the apparatus out to remove the accretion is necessary.However, in the maintenance operation, since it is difficult to pull outthe portion of apparatus, the maintenance operation takes a lot of time.

Furthermore, similarly to the Japanese Unexamined Patnt ApplicationPublication No. 58-189335, the additional coating auxiliary raw materialis widely scattered in the drum mixer and reaches up to the charge sideof the drum mixer. The auxiliary raw material scattered up to the chargeside is taken in the sintering material in the course of the granulationby the drum mixer, accordingly there is a problem in that the additionalcoating auxiliary raw material cannot be deposited onto the pseudoparticle surface.

The present invention was carried out to overcome the above-mentionedconventional problems and intends to provide a manufacturing method of amaterial for sintering that can improve the cold strength and thereducibility of the sintered ore and apparatus therefor. The inventivemanufacturing method includes, as a pre-treatment of a process ofmanufacturing sintered ore, without necessitating huge apparatus,forming pseudo particles by granulating iron ore M1 and SiO₂-containingmaterial M2 separately from limestone base material M3 and solid fueltype material M4; and selecting a time to additionally coat limestonebase material M3 and solid fuel type material M4 to gradually formpseudo particles, and thereby manufacturing sintered ore having astructure in which a layer rich in the limestone base material M3 andsolid fuel type material M4 is formed on a surface portion of the pseudoparticle, calcium ferrite (CF) high in the strength is generated on thesurface of the sintered ore, and on the other hand toward the inside ofthe sintered ore, hematite (He) high in the reducibility is selectivelyformed.

In the present invention, iron ore of material for sintering includescoarse, powdery iron ore and returned ore that is again utilized as thesintering material, and with these generically referring as iron ore,the invention will be explained.

DISCLOSURE OF THE INVENTION

A first aspect of the invention for achieving the above object is amanufacturing method of a material for sintering. The manufacturingmethod is characterized in that when, with a Dwight-Lloyd type sinteringmachine of downward suction, as a pretreatment of a manufacturingprocess of sintered ore for use in a blast furnace, sintering materialincluding iron ore M1, SiO₂-containing material M2, limestone basepowdery material M3 and solid fuel type powdery material M4 isgranulated by means of a drum mixer, the sintering material exceptingthe limestone base powdery material M3 and solid fuel type powderymaterial M4 is charged from a charge inlet of the drum mixer togranulate, and, in a region disposed in the middle on a downstream sidewhere a staying time during which the sintering material reaches up toan exhaust outlet of the drum mixer is in the range of from 10 to 90seconds, the limestone base powdery material M3 and solid fuel typepowdery material M4 are added, and thereby until reaching the exhaustoutlet, the limestone base powdery material M3 and solid fuel typepowdery material M4 (hereinafter in the invention, limestone basepowdery material M3 and solid fuel type powdery material M4 are referredto as additional coating auxiliary raw material 8) are deposited andformed on the exterior coating portion of the sintering material.

Furthermore, a second aspect of the invention is a manufacturing methodof material for sintering characterized in that, in the first aspect,the sintering material excepting the limestone base powdery material M3and solid fuel type powdery material M4 is charged from a charge inletof the drum mixer to granulate, and, in a region disposed in the middleon a downstream side where a staying time during which the sinteringmaterial reaches an exhaust outlet of the drum mixer is in the range offrom 10 to 90 seconds, after the limestone base powdery material M3 isadded, the solid fuel type powdery material M4 is added, and therebyuntil reaching the exhaust outlet, the limestone base powdery materialM3 and the solid fuel type powdery material M4 are deposited in turn andformed on the exterior coating portion of the sintering material.

Still furthermore, a third aspect of the invention is a manufacturingmethod of material for sintering characterized in that, in the first andsecond aspects, the drum mixer is divided into a plurality of drummixers, a final drum mixer is made to have a drum mixer length disposedso that a staying time from the charge inlet up to the exhaust outletmay be in the range of from 10 to 90 seconds.

Furthermore, a fourth invention is a manufacturing method of materialfor sintering characterized in that, in the first and second aspects,the drum mixer is divided into a plurality of drum mixers, in a regiondisposed in the middle on a downstream side where a staying time duringwhich the sintering material reaches up to an exhaust outlet of thefinal drum mixer is in the range of from 10 to 90 seconds, the limestonebase powdery material M3 and solid fuel type powdery material M4 areadded, and thereby until reaching the exhaust outlet, the limestone basepowdery material M3 and solid fuel type powdery material M4 aredeposited and formed on the exterior coating portion of the sinteringmaterial.

Still furthermore, a fifth aspect of the invention is a manufacturingapparatus of a sintering material characterized in that in amanufacturing apparatus including a drum mixer by which a sinteringmaterial is, while rolling and transferring, formed into pseudoparticles; and a additional coating conveyer that projects theadditional coating auxiliary raw material 8 in the middle of formingpseudo particles of the sintering material into the drum mixer, on anexhaust outlet side of the drum mixer, a additional coating conveyer isdisposed so that an exhaust end thereof faces the exhaust outlet of thedrum mixer.

Furthermore, a sixth aspect of the invention is characterized in that,in the fifth aspect, the additional coating conveyer can control aninitial speed and/or an angle of elevation of a additional coatingauxiliary raw material 8 when the additional coating auxiliary rawmaterial 8 is projected into the drum mixer.

Still furthermore, a seventh aspect of the invention is a manufacturingapparatus of a sintering material characterized in that, in the fifthaspect, movement means for moving the additional coating conveyer sothat the exhaust end of the additional coating conveyer may move betweena predetermined position on an exhaust outlet side inside of the drummixer and a position outside of the exhaust outlet of the drum mixer aredisposed.

Furthermore, an eighth aspect of the invention is a manufacturingapparatus of a sintering material characterized in that, in the sixth orseventh aspect, speed control means for controlling a belt speed of theadditional coating conveyer is disposed, and thereby a projectioninitial speed of the additional coating auxiliary raw material 8 that isprojected into the drum mixer is made controllable.

Still furthermore, a ninth aspect of the invention is a manufacturingapparatus of a sintering material characterized in that, in the eighthaspect, a predetermined position on an exhaust outlet side inside of thedrum mixer where the exhaust end of the additional coating conveyer islocated and the belt speed of the additional coating conveyer arecontrolled so that the projection position of the additional coatingauxiliary raw material 8 may be a region disposed in the middle on adownstream side where a staying time of the sintering material untilreaching the exhaust outlet of the drum mixer is in the range of from 10to 90 seconds.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram of mixing and granulating a sinteringmaterial involving a conventional example.

FIG. 2 is a diagram showing relationship between the reducibility JIS-RI(%) of a sintered ore and gas utilization factor η_(co) (%) in a blastfurnace.

FIG. 3 is a diagram showing relationship between the gas utilizationfactor η_(co) (%) and the fuel ratio (kg/t-pig) in a blast furnace.

FIG. 4 is a diagram explaining a texture structure of a desirablesintered ore in the invention.

FIG. 5 is a diagram explaining a pseudo particle structure and a texturestructure of a sintered ore according to a conventional example.

FIG. 6 is a diagram explaining a method of exterior coating experimentof a limestone base powdery material and a solid fuel type powderymaterial.

FIG. 7 is a characteristic diagram showing relationship between exteriorcoating period of time vs. the reducibility JIS-RI (%) and pore volume(cc/g) of the sintered ore.

FIG. 8 is a diagram showing distributions of Ca and Fe in a pseudoparticle when the exterior coating period of time is varied.

FIG. 9 is a diagram schematically explaining a mode for carrying out thepresent invention.

FIG. 10 is a diagram showing a mode for carrying out the invention(method A).

FIG. 11A is a diagram showing another mode for carrying out theinvention (method B).

FIG. 11B is a diagram showing another mode for carrying out theinvention (method B).

FIG. 12A is a diagram showing still another mode for carrying out theinvention (method C).

FIG. 12B is a diagram showing still another mode for carrying out theinvention (method C).

FIG. 13 is a diagram showing pore distribution in the sintered oreaccording to the invention in comparison with that of a conventionalexample.

FIG. 14 is a diagram showing measurements by EPMA of cross sections ofsintered bodies of pseudo particles according to the inventive and theconventional methods.

FIG. 15 is a diagram showing the reducibility JIS-RI (%), yield andproductivity involving the invention in comparison with those of theconventional example.

FIG. 16 is a side view showing an outline of manufacturing apparatus ofthe sintering material involving one mode for carrying out theinvention.

FIG. 17A is a plan view showing one example of means for expanding arange of dispersion of an additional coating auxiliary raw material.

FIG. 17B includes a plan view and a partial sectional view showinganother example of means for expanding a range of dispersion of anadditional coating auxiliary raw material.

FIG. 18 is a side view on a side of a drum mixer exhaust outlet of themanufacturing apparatus of the sintering material when an exhaust end ofan additional coating conveyer is located at a predetermined position ona side of exhaust outlet in a drum mixer.

FIG. 19 is a side view on a side of a drum mixer exhaust outlet of themanufacturing apparatus of the sintering material when an exhaust end ofan additional coating conveyer is located outside of an exhaust outletof the drum mixer.

FIG. 20 is an arrow A-A sectional view in FIG. 18.

FIG. 21 is a schematic side view of apparatus for projection experimentof an additional coating auxiliary raw material.

FIG. 22 is a graph comparing measurements and calculated values ofprojection distance.

FIG. 23 is a graph showing investigation results of dispersibility whenan additional coating auxiliary raw material of a transfer amount of 8kg/s (coke: 3 kg/s and limestone: 5 kg/s) is projected at a belt speedof 300 m/s and an angle of elevation of 0 degree.

FIG. 24 is a side view showing an outline of the manufacturing apparatusof the sintering material when the exhaust end of an additional coatingconveyer is positioned outside of an exhaust outlet of the drum mixer.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, situations that led to the completion of the presentinvention and a gist of specific modes for carrying out the inventionwill be explained with reference to the drawings.

In the invention, it was found that when a time for adding in particulara limestone base powdery material M3 and a solid fuel type powderymaterial M4 to deposit and form on a exterior coating portion of asintering material was set, that is, when after the limestone basepowdery material M3 and solid fuel type powdery material M4 areadditionally coated and added to the sintering material that is beinggranulated, a staying time after the addition until the sinteringmaterial reaches the exhaust outlet of the drum mixer, so-calledgranulation period of time (hereinafter simply referred to as “exteriorcoating time”) after the limestone base powdery material M3 and solidfuel type powdery material M4 are added to deposit and form on theexterior coating portion of the sintering material was set, the effectwas largely different.

As shown in FIG. 6, an experiment was carried out in such way that withthe granulation period of time of the sintering material (the iron oreM1 and SiO₂-containing material M2) excepting the limestone base powderymaterial M3 and solid fuel type powdery material M4 fixed constant (240seconds), the exterior coating period of time of the limestone basepowdery material M3 and solid fuel type powdery material M4 was variedfrom 60 seconds to 360 seconds.

As a result, as shown in FIG. 7, it was found that as the exteriorcoating period of time became longer, fine pores of 0.5 mm or lesseffective in an improvement in the reducibility decreased, thereducibility deteriorated, and the exterior coating period of time wasdesirably 90 seconds or less. Measurement of the pore volume wasperformed by a mercury push-in method with a mercury porosimeter.Furthermore, from another experiment, it was found that when theexterior coating period of time was less than 10 seconds, because ofinsufficiency of the exterior coating period of time, added limestonebase powdery material and solid fuel type powdery material partiallysegregated, a uniform sintered state could not be obtained, and aneffect according to the invention was not exhibited.

Here, a exterior coating region inside of the mixer where the exteriorcoating period of time is from 10 to 90 seconds corresponds to, in termsof the number of revolution of the sintering material in the drum mixer,2 to 36 revolutions, and to 0.5 to 5 m from exhaust outlet end 35 of thedrum mixer 4. However, as far as the exterior coating period of time inthe mixer is controlled so as to be in the range of from 10 to 90seconds, a dimension of the exterior coating region is not restricted tothe above dimension.

In FIG. 8, results of distribution investigation of Ca and Fe in pseudoparticles of the sintering material by electron probe microanalysis(hereinafter simply referred to as EPMA) are shown. Therefrom, it can beconfirmed that when the exterior coating period of time is properly set(60 seconds in this experiment), the distribution of Ca becomesouter-ring like; that is, exterior coating is achieved. On the otherhand, when the exterior coating period of time is made longer (360seconds in the comparative example), particles are destroyed in the drummixer and limestone is contained in the pseudo particles. As a result,Ca distributes at large and there is no difference from the conventionalmethod.

In other words, since in the drum mixer, not only the granulation butalso the destruction of the pseudo particles simultaneously proceeds,when the exterior coating period of time is set longer than necessary,the limestone base powdery material M3 and solid fuel type powderymaterial M4 that are added to externally coat are contained owing to thedestruction of the pseudo particles and exist in both inner and outerexterior coating. It is confirmed that, as a result, sintered ore havinga structure in which on the surface of the sintered ore calcium ferrite(CF) high in the strength is generated, on the other hand toward theinside of the sintered ore hematite (He) high in the reducibility isselectively formed cannot be obtained. That is, proper selection of theexterior coating period of time was found to be important.

Furthermore, as mentioned above, when the exterior coating period oftime is set too short, the added limestone base powdery material M3 andsolid fuel type powdery material M4 segregate in the sintering material,resulting in non-uniform sintering of the sintering material on thesintering machine. Then, the inventors investigated the exterior coatingperiod of time that does not cause the segregation; as a result, it wasfound that the exterior coating period of time of 10 seconds or more wasnecessary. That is, there is a disadvantage in that the exterior coatingperiod of time is under stringent condition, and simple addition of theauxiliary raw material in a later half portion in the drum mixer allowscontaining the auxiliary raw material inside of the pseudo particle.

When the condition on the exterior coating period of time according tothe invention is satisfied, the limestone base powdery material M3 andsolid fuel type powdery material M4 can be for the first time externallycoated without being contained inside thereof (inner exterior coating);accordingly, a material for sintering is manufactured with, inside ofthe pseudo particle, the SiO₂-containing material M2 separated from thelimestone base powdery material M3, that is, without limestone. Thereby,CaO and SiO₂ are delayed in the reaction, resulting in suppressingcalcium silicate (CS) poor in the reducibility and low in the coldstrength from generating.

In the invention, at the interface between the exterior coated limestonebase powdery material and iron ore, a calcium ferrite (CF) system meltis formed and covers a circumference of the iron ore, resulting inexhibiting sufficient cold strength. When sintering is performed withthis material for sintering, a sintered ore in which calcium ferrite(CF) high in the strength is formed on the surface of the sintered oreand hematite (He) high in the reducibility is selectively formed towardthe inside of the sintered ore can be formed.

An example of granulation flow (method A) according to the invention isshown in FIGS. 9 and 10. As shown in FIG. 9, from a charge side of thedrum mixer 4, a sintering material (iron ore M1 and SiO₂-containingmaterial M2) excepting limestone and powdery coke that are,respectively, the limestone base powdery material M3 and solid fuel typepowdery material M4 is charged, and in order to control the exteriorcoating period of time, the limestone and powdery coke are added fromexhaust side 35 of the drum mixer.

As mentioned above, in order to obtain the sintering material adequatefor the sintered ore, an additional coating position in the drum mixer 4of the auxiliary raw material that is the limestone base powderymaterial M3 and solid fuel type powdery material M4 is important. Whenthe additional coating position of the auxiliary raw material is in aforward end portion in the drum mixer 4, since the pseudo particles thatbecome seed particles have not been sufficiently formed and grown,additionally coated auxiliary raw material is taken into the inside ofthe pseudo particles. On the other hand, even when the additionalcoating position of the auxiliary raw material is in an intermediateportion in the drum mixer 4, since in the drum mixer 4, the granulationaction (formation of pseudo particles) of the sintering material and thedestruction action thereof are simultaneously proceeding, the additionalcoating auxiliary raw material 8 is taken into the inside of thedestroyed pseudo particles. Accordingly, the object to manufacturepseudo particles having a three-layer structure with a layer rich inpowdery coke in the outer-most layer cannot be achieved. Furthermore,when the additional coating position of the auxiliary raw material istoo close to a back end portion in the drum mixer 4, the additionallycoating auxiliary raw material does not uniformly adhere to theouter-most layer of the pseudo particles, in some cases, remainscoagulated without adhering, resulting in disturbing a smooth proceedingof the sintering. Accordingly, it is better to additionally coat theauxiliary raw material in a region disposed in the middle on adownstream side where a staying time until the sintering materialreaches the exhaust outlet 35 of the drum mixer is in the range of from10 to 90 seconds.

Such additional coating can be performed by projecting the additionalcoating auxiliary raw material 8 from back end portion 35 of the drummixer. However, as shown in FIG. 16, it is better to dispose additionalcoating conveyer 10 that can project the additional coating auxiliaryraw material 8 from an exhaust end D of the additional coating conveyer10 in proximity to the exhaust outlet of the drum mixer to apredetermined range in the drum mixer to additionally coat. FIG. 10shows a preferable specific example thereof, and in the example, inaccordance with a exterior coating region disposed in the middle on adownstream side of the drum mixer 4 where a staying time until thematerial for sintering reaches the exhaust outlet 35 is in the range offrom 10 to 90 seconds, a tip end position D of the belt conveyer 10disposed freely movable from the exhaust outlet 35 on the downstreamside in a longer direction in the drum mixer 4 is controlled so as toposition in an intermediate position of the exterior coating region thatcorresponds to, for instance, 60 seconds in the range of from 10 to 90seconds.

Subsequently, through the belt conveyer 10, the limestone base powderymaterial M3 (for instance, powdery limestone) and solid fuel typepowdery material M4 (for instance, powdery coke) are added to apredetermined region (here, an intermediate position of the exteriorcoating region), and pseudo particles having a exterior coating portionwhere on circumference of pseudo particles formed by granulation untilreaching the exterior coating region in the drum mixer 4, the limestonebase powdery material M3 and solid fuel type powdery material M4 aredeposited and formed are granulated. The limestone base powdery materialM3 and solid fuel type powdery material M4, when an average particlesize is made 1.5 mm or less and preferably 1.0 mm or less, can adhere tothe exterior coating portion with ease and can cover outer surfacethereof. The method A is a case where a single drum mixer is used.

Furthermore, in FIGS. 11A and 11B, an example of granulation flow(method B) according to which a desirable pseudo particle structureaccording to another invention is manufactured is shown. The example ofgranulation flow (method B) is an example in which the drum mixer 4shown in FIG. 10 is divided into a plurality of sections in a longerdirection, in the present example a two-division type being shown. InFIG. 11A, a first drum mixer 4A where the sintering material exceptingthe limestone base powdery material M3 and solid fuel type powderymaterial M4 is charged and granulated to obtain pseudo particles, and asecond drum mixer 4B where pseudo particles having a exterior coatingportion where on the circumference of the pseudo particles granulated inthe first drum mixer 4A, the limestone base powdery material M3 andsolid fuel type powdery material M4 are deposited are granulated aredisposed in series. The first drum mixer 4A has a length during whichpseudo particles can be granulated, and the second drum mixer 4B has alength during which on the outer periphery of the pseudo particle thelimestone base powdery material M3 and solid fuel type powdery materialM4 that is a heat source can be exterior coated and deposited. That is,the length of the second drum mixer 4B has a dimension corresponding tothe exterior coating region where a staying time of the pseudo particleuntil the pseudo particle reaches from the charge inlet to exhaustoutlet 35 is in the range of from 10 to 90 seconds.

In this case, from a charge inlet of the first drum mixer 4A, iron oreM1 and SiO₂-containing material M2 (material containing relatively muchSiO₂ such as silica rock, serpentine rock, and Ni slag) excepting thelimestone base powdery material M3 and solid fuel type powdery materialM4 are charged. While repeating the granulation and destruction in thecourse until reaching from the charge inlet of the first drum mixer 4Ato the exhaust outlet, with a coarse particle of iron ore M1 as a seedparticle and with fine particles of iron ore and the SiO₂-containingmaterial M2 deposited on the circumference of the coarse particle ofiron ore, a pseudo particle is granulated. Thereafter, when the pseudoparticles are charged into a charge inlet of the second drum mixer 4B,the limestone base powdery material M3 and solid fuel type powderymaterial M4 that becomes a heat source are fed to a charge inlet of thesecond drum mixer 4B. Thereby, in the second drum mixer 4B, on thecircumference of the pseudo particles, the limestone base powderymaterial M3 and solid fuel type powdery material M4 are exterior coatedand deposited, and thereby the granulation is performed.

In FIG. 11B, an application example of the invention where the existingdrum mixer 4 is divided into two sections is shown. When a length of adrum mixer 4B that is a later half portion is longer than a length thatcorresponds to 90 seconds of the exterior coating time, similarly to theexample shown in FIG. 10, from an exhaust side of the drum mixer 4B ofthe later half portion, by means of belt conveyer 10, in the exteriorcoating region, the limestone base powdery material M3 and solid fueltype powdery material M4 that becomes a heat source are supplied andadded.

Furthermore, FIGS. 12A and 12B show specific examples of a manufacturingmethod (method C) of a material for sintering where in the exteriorcoating region disposed in the middle on a downstream side of whichstaying time is in the range of from 10 to 90 seconds, after thelimestone base powdery material M3 is added, the solid fuel type powderymaterial M4 is added, and during reaching the exhaust outlet 35, on theexterior coating portion of the pseudo particle of the sinteringmaterial, the limestone base powdery material M3 and solid fuel typepowdery material M4 are in this order deposited and formed. FIG. 12Ashows a mode where from exhaust side 35 of a single drum mixer 4 to theexterior coating region, the limestone base powdery material M3 andsolid fuel type powdery material M4 that becomes a heat source,respectively, are supplied and added by use of belt conveyers 10A and10B. Furthermore, FIG. 12B shows a specific example when a drum mixer isdivided into two. In this mode, at a charge side of the drum mixer 4Bdisposed to be a dimension corresponding to a exterior coating region inthe range of from 10 to 90 seconds, the limestone base powdery materialM3 is supplied and added, and from the exhaust side 35 of the drum mixer4B to the exterior coating region, by means of the belt conveyer 10, thesolid fuel type powdery material M4 that becomes a heat source issupplied and added. By adding to the exterior coating region, on theexterior coating portion of the pseudo particle, the limestone basepowdery material M3 and solid fuel type powdery material M4 aresuccessively deposited and formed. In this addition mode, when after theaddition of the limestone base powdery material M3, the solid fuel typepowdery material M4 is added at a position having a time difference ofmore than 10 seconds, on the exterior coating portion of the pseudoparticle, after an adhesion layer of the limestone base powdery materialM3 is formed, the solid fuel type powdery material M4 is furtherdeposited and formed.

According to (method A) or (method B) of the invention, with a coarseiron ore M1 as a seed particle, to the periphery thereof fine iron oreM1 and SiO₂-containing material M2 can be deposited, furthermore in theperiphery thereof the limestone base powdery material M3 and solid fueltype powdery material M4 (coke) that becomes a heat source can bedeposited and formed to the exterior coating portion. Furthermore,according to the (method C) of the invention, when the limestone basepowdery material M3 and solid fuel type powdery material M4 (coke) thatbecomes a heat source are deposited and formed on the exterior coatingportion, the solid fuel type powdery material M4 (coke) that becomes aheat source can be deposited and formed on the outer-most exteriorcoating portion.

Thereby, in the invention, from a charge inlet of the drum mixer 4 thesintering material excepting the limestone base powdery material M3 andsolid fuel type powdery material M4 is charged to granulate and in aregion disposed in the middle on a downstream side where a staying timeduring which the sintering material reaches the exhaust outlet 35 of thedrum mixer 4 is in the range of from 10 to 90 seconds the limestone basepowdery material M3 and solid fuel type powdery material M4 are added.Accordingly, according to the inventive method, since until reaching theexhaust outlet 35, the limestone base powdery material M3 and solid fueltype powdery material M4 can be deposited and formed on the exteriorcoating portion of the sintering material, in the course of sintering ofthe material for sintering, a reaction between CaO and SiO₂ belatedlyoccurs, resulting in suppressing calcium silicate (CS) low in the coldstrength from generating. As a result, on the surface of the sinteredore calcium ferrite (CF) high in the strength is generated, and towardthe inside of the sintered ore hematite (He) high in the reducibility isselectively generated. Thereby, the sintered ore rich in fine pores,excellent in the reducibility and high in the cold strength can bestably manufactured.

Furthermore, in a method of manufacturing material for sintering whereas a pretreatment to the process according to which sintered ore for ablast furnace is manufactured by use of a Dwight-Lloyd type sinteringmachine of downward suction, when a sintering material including ironore M1, SiO₂-containing material M2, limestone base powdery material M3and solid fuel type powdery material M4 is granulated by use of the drummixer 4, from the charge inlet of the drum mixer 4, the sinteringmaterial excepting the limestone base powdery material M3 and solid fueltype powdery material M4 is charged and granulated and in a regiondisposed in the middle on a downstream side where a staying time duringwhich the sintering material reaches the exhaust outlet 35 of the drummixer 4 is in the range of from 10 to 90 seconds the limestone basepowdery material M3 is added followed by adding the solid fuel typepowdery material M4, and thereby during reaching the exhaust outlet, onthe exterior coating portion of the sintering material, the limestonebase powdery material M3 and solid fuel type powdery material M4 aredeposited and formed in this order, as mentioned above, toward theinside of the sintered ore hematite (He) high in the reducibility isselectively generated and the sintered ore rich in the fine pores,excellent in the reducibility and high in the cold strength can bestably manufactured, in addition, the solid fuel type powdery materialM4 that becomes a heat source can be deposited and formed on theouter-most portion of the exterior coating portion, resulting inobtaining an improvement in the combustibility of the added solid fueltype powdery material M4.

In the next place, manufacturing apparatus will be explained.

FIG. 16 is a side view showing an outline of manufacturing apparatus ofa sintering material involving one mode for carrying out the invention.

In FIG. 16, manufacturing apparatus 1 of the sintering material includesraw material conveyer 2 that transfers sintering material 7, shoot 3that equally divides the transferred sintering material 7 excepting thelimestone base powdery material M3 and solid fuel type powdery materialM4 into drum mixer 4, drum mixer 4 that while rolling and transferringthe sintering material 7 forms pseudo particles, additional coatingconveyer 10 that projects additional coating auxiliary raw material (thelimestone base powdery material M3 and solid fuel type powdery materialM4) 8 into the drum mixer 4 in the middle of forming the pseudoparticles of the sintering material 7, hood (exhaust fan) 5 forexhausting dust powder from the inside of the drum mixer 4, and oreexhaust conveyer 6 by which sintering material 9 after formation of thepseudo particles is transferred to a sintering machine. The additionalcoating conveyer 10 and ore exhaust conveyer 6 are disposed in proximityto the exhaust outlet 35 of the drum mixer 4. The sintering material 7generally, includes the SiO₂-containing material M2 that includes ironore (including returned ore), silica rock, serpentine rock or nickelslag having a particle size of 10 mm or less. On the other hand, theadditional coating auxiliary raw material 8 includes the CaO containinglimestone base powdery material M3 such as calcined lime, limestone andso on and the solid fuel type powdery material M4 that becomes a heatsource such as powdery coke or anthracite coal.

In the next place, an example of the apparatus according to theinvention will be detailed. In the apparatus shown in FIG. 16, theadditional coating conveyer 10 is provided with transfer means 32 fortransferring the additional coating conveyer 10 in a directionsubstantially along a longer direction of the drum mixer 4, the exhaustend D of the additional coating conveyer 10 being disposed so as to movebetween a predetermined position (forwarding position) on an exhaustoutlet side in the drum mixer 4 and an outside position (recedingposition shown with a chain double-dashed line) of the exhaust outlet 35of the drum mixer 4. The exhaust end D of the additional coatingconveyer 10 can be stopped at an arbitrary position between theforwarding position and the receding position.

A configuration of the transfer means 32 will be detailed with referenceto FIGS. 18 through 20. FIG. 18 is a side view of an exhaust outlet sideof the drum mixer 4 of the manufacturing apparatus of the sinteringmaterial when the exhaust end D of the additional coating conveyer 10 islocated at a predetermined position on the exhaust outlet side in thedrum mixer 4, FIG. 19 being a side view of an exhaust outlet side of thedrum mixer of the manufacturing apparatus of the sintering material whenthe exhaust end D of the additional coating conveyer 10 is locatedoutside of the exhaust outlet 35 of the drum mixer 4, FIG. 20 being anA-A arrow sectional view of FIG. 18.

The additional coating conveyer 10, as shown in FIGS. 18 and 19,includes conveyer body 11 extending anteroposteriorly substantiallyalong a longer direction of the drum mixer 4, the exhaust end D (forwardend) of the conveyer body 11 being provided with freely rotatable pulley12, end portion C (back end portion) on a side opposite to the exhaustend of the conveyer body 11 being provided with driving pulley 13. Theadditional coating conveyer 10, as shown in FIG. 20, is positioned sothat a centerline CL in a width direction thereof may be placed shiftedby a distance e with respect to a centerline CL of the drum mixer 4. Tothe driving pulley 13, driving motor 33 (FIG. 16) for rotating anddriving the driving pulley 13 is connected. On an exterior periphery ofpulley 12 and the driving pulley 13, endless belt 14 is wound, and thebelt 14 is driven by rotation and drive of the driving pulley 13. To thedriving motor 33, speed control means 34 (FIG. 16) for controlling thespeed of the belt 14 of the additional coating conveyer 10 is connected,and an initial projection speed of the additional coating auxiliary rawmaterial 8 that is projected into the drum mixer 4 is made controllable.Then, at a substantial center portion in a longer direction of theconveyer body 11, through a plurality of pillars 17, a pair of wheels 19is disposed, and at the backward end portion C of the conveyer body 11,through a plurality of pillars 18, a pair of wheels 20 is disposed.These wheels 19 and 20 are disposed movable in an anteroposteriordirection on rail 21. At a forward end of the rail 21, forward stopper22 that limits a forward movement of the wheels 19 disposed in a frontside is disposed, and at a backward end of the rail 21, backward stopper23 that limits a backward movement of the wheels 20 disposed in a backside is disposed. Furthermore, on base 25 erected from the ground,rotation drum 26 connected to not shown rotation control means isdisposed. Around the rotation drum 26, wire 29 is wound, one end portionof the wire 29 being engaged through front pulley 27 to engaging portion30 disposed in front of the pillar 18, on the other hand, the other endportion of the wire 29 being engaged through rear pulley 28 to engagingportion 31 disposed in back of the pillar 18. The pillars 17, 18, wheels19, 20, rail 21, stoppers 22, 23, base 25, rotation drum 26, front andrear pulleys 27, 28 and wire 29 constitute the transfer means 32. InFIGS. 18 through 20, reference numerals 15, 16 denote transfer rollers.

In the next place, operations of the manufacturing apparatus 1 of thesintering material will be explained with reference to FIGS. 16 through20.

The sintering material 7 transferred by the raw material conveyer 2 isequally divided by the shoot 3 and charged into the drum mixer 4 fromthe charge inlet thereof. Then, the sintering material 7, rolling in thedrum mixer 4 toward a right direction in FIG. 16, with a coarse particleas a seed particle and with fine particles depositing on the peripheryof thereof, the formation of the pseudo particles proceeds.

At a position that is a substantial final step of the formation of thepseudo particle, that is, at a position in the neighborhood of theexhaust outlet 35 of the drum mixer 4, as shown with an arrow mark inFIGS. 16 and 20, to the sintering material 7 that is forming pseudoparticles, the additional coating auxiliary raw material 8 is projectedfrom the additional coating conveyer 10. At this time, so that theexhaust end D of the additional coating conveyer 10 may be positioned ata predetermined position (a full line position in FIG. 16, a position ofFIG. 18) on a side of the exhaust outlet 35 in the drum mixer 4, theadditional coating conveyer 10 has been moved by use of the transfermeans 32. By this additional coating operation, the additional coatingauxiliary raw material 8 is deposited on the exterior coating portion ofthe pseudo particle, and thereby an outer shell of the pseudo particleis formed. When the outer shell of the pseudo particle is formed, theshape stability and an improvement in the strength of the pseudoparticle result.

The predetermined position on a side of the exhaust outlet 35 in thedrum mixer 4 where the exhaust end D of the additional coating conveyer10 is positioned and the speed of the belt 14 of the additional coatingconveyer 10 are preferably controlled so that a projection position ofthe additional coating auxiliary raw material 8 may be in a regiondisposed in the middle on a downstream side where a staying time duringwhich the sintering material 7 reaches the exhaust outlet of the drummixer 4 is in the range of from 10 to 90 seconds. Thereby, in the courseof sintering of the sintering material, a reaction between CaO and SiO₂occurs belatedly, calcium silicate (CS) low in the cold strength beingsuppressed from generating, calcium ferrite (CF) strong in the strengthbeing generated on a surface of the sintered ore, hematite (He) high inthe reducibility being selectively generated toward the inside of thesintered ore, the sintered ore rich in the fine pores, excellent in thereducibility, and high in the cold strength being stably manufactured.

Furthermore, from the viewpoint of safety, when the projection of theadditional coating auxiliary raw material 8 is continued, since theexhaust end D of the additional coating conveyer 10 is inside of thedrum mixer 4, dust powder (calcined lime and so on) in the drum mixer 4adheres and solidly sticks to the exhaust end D of the additionalcoating conveyer 10, resulting in causing disturbance in conveyeroperation. Accordingly, when the dust powder in the drum mixer 4 adheresa certain extent to the exhaust end D of the additional coating conveyer10, an operator rotates the rotation drum 26 by rotation control meansin a direction shown by an arrow mark a in FIG. 18 to draw out theadditional coating conveyer 10 in an arrow mark direction b in FIG. 18,and thereby, as shown in FIG. 19, the exhaust end D of the additionalcoating conveyer 10 is made to locate at a position outside of theexhaust outlet 35 of the drum mixer 4 (chain double-dashed line positionin FIG. 16). When the rotation drum 26 is rotated in a direction shownby the arrow mark a, a portion locating behind the rotation drum 26 ofthe wire 30 twines around the rotation drum 26, the additional coatingconveyer 10 being moved through the wire 30 in an arrow mark bdirection. Then, as shown in FIG. 19, in a state where the exhaust end Dof the additional coating conveyer 10 is located outside of the exhaustoutlet 35 of the drum mixer 4, the operator cleanses a portion of theadditional coating conveyer 10 thereto dust powder adhered and removesthe accretion.

After the cleaning came to completion, the operator, by use of therotation control means, rotates the rotation drum 26 in a directionshown by an arrow mark c in FIG. 19 to move the additional coatingconveyer 10 in a direction shown by an arrow mark d in FIG. 19, andthereby, as shown in FIG. 18, the exhaust end D of the additionalcoating conveyer 10 is made to locate at a predetermined position on theexhaust outlet side of the drum mixer 4. When the rotation drum 26 isrotated in a direction shown by the arrow mark c, a portion locating infront of the rotation drum 26 of the wire 30 twines around the rotationdrum 26, the additional coating conveyer 10 being moved through the wire30 in a direction shown by an arrow mark d. Then, as shown in FIG. 18,in a state where the exhaust end D of the additional coating conveyer 10is located at a predetermined position on the exhaust outlet side in thedrum mixer 4, the additional coating auxiliary raw material 8 isprojected.

Thus, in the manufacturing apparatus 1 of the sintering material shownin FIGS. 16 through 20, the transfer means 32 for transferring theadditional coating conveyer 10 is disposed so that the exhaust end D ofthe additional coating conveyer 10 may move between a predeterminedposition on the exhaust outlet side in the drum mixer 4 and a positionoutside of the exhaust outlet 35 of the drum mixer 4, accordingly, atthe maintenance operation by which the accretion adhered to theadditional coating conveyer 10 is removed, the additional coatingconveyer 10 can be easily drawn out, resulting in easily performing themaintenance operation within a short time.

As shown in FIG. 16, speed control means 34 for controlling the speed ofthe belt 14 of the additional coating conveyer 10 is disposed so as toenable to control an initial projection speed of the additional coatingauxiliary raw material 8 that is projected into the drum mixer 4.Accordingly, when a position on the exhaust outlet side in the drummixer 4 wherein the exhaust end D of the additional coating conveyer 10is positioned is made closer to the exhaust outlet 35 and the initialprojection speed of the additional coating auxiliary raw material 8 ismade faster when the additional coating auxiliary raw material 8 isprojected, a projection position of the additional coating auxiliary rawmaterial 8 can be made the same state as that when the initialprojection speed is made slower. As a result, the position on theexhaust outlet side in the drum mixer 4 wherein the exhaust end D of theadditional coating conveyer 10 is positioned can be made closer to theexhaust outlet 35, accordingly, an adhering speed of the accretion thatadheres to the additional coating conveyer 10 can be made slower and thefrequency of the maintenance operation for removing the accretionadhered to the additional coating conveyer 10 can be made smaller.

On the other hand, in order to inhibit the dust powder from adhering tothe exhaust end D of the additional coating conveyer 10, as shown inFIG. 24, by positioning the exhaust end D of the additional coatingconveyer 10, without inserting into the drum mixer 4, always outside ofthe exhaust outlet 35 of the drum mixer 4, and by projecting with alarger initial projection speed of the additional coating auxiliary rawmaterial 8 that is projected into the drum mixer 4, the additionalcoating auxiliary raw material 8 can be allowed to reach inside of thedrum mixer to additionally coat.

In the above, modes for carrying out the invention were explained;however, the present invention, without restricting thereto, may bevariously changed and improved.

For instance, the transfer means 32 shown in FIGS. 18 and 19, as far asit can move the additional coating conveyer 10 so that the exhaust end Dof the additional coating conveyer 10 may move between a predeterminedposition on the exhaust outlet side in the drum mixer 4 and a positionoutside of the exhaust outlet 35 of the drum mixer 4, need not includethe pillars 17, 18, wheels 19, 20, rail 21, stoppers 22, 23, base 25,rotation drum 26, front and rear pulleys 27, 28, and wire 29.

Furthermore, as far as a additional coating mode where the additionalcoating conveyer 10 is inserted (intruded) into the drum mixer 4 toadditionally coat is taken, the speed control means 34 for controllingthe speed of the belt 14 of the additional coating conveyer 10 is notnecessarily disposed.

In the additional coating experiment of the auxiliary raw material, thebelt conveyer 10 is not provided with an angle of elevation, however,the additional coating conveyer 10 is preferably provided with elevationangle control means so that not only the initial speed but also theelevation angle may be controlled. Furthermore, when a additionalcoating angle of the additional coating conveyer 10 and/or a additionalcoating position in a width direction in the drum mixer 4 is madevariable, a dispersion range of the additional coating auxiliary rawmaterial 8 can be preferably widened. In FIG. 17, an example of meansfor expanding a dispersion range of the additional coating auxiliary rawmaterial is shown. FIG. 17A is a plan view showing a case where byadditionally coating with the additional coating conveyer 10 disposedslanted to an axial direction of the drum mixer 4, a dispersion range ofthe additional coating auxiliary raw material 8 is expanded. FIG. 17B isa plan view and an A-A arrow sectional view showing a case where bydisposing the additional coating conveyer 10 decentered from a centeraxis of the drum mixer 4 to additionally coat, a dispersion range of theadditional coating auxiliary raw material 8 is expanded.

EMBODIMENTS Embodiment 1

Pseudo particles that had been granulated according to the granulationflow (method A) of the invention from a sintering material having acompounding ratio shown in Table 2 were transferred to a Dwight-Lloydtype sintering machine and charged on a palette. For comparison, pseudoparticles that had been granulated according to a treatment method whereiron ore M1, SiO₂-containing material M2, limestone base material M3 andcoke powder M4 are simultaneously mixed were transferred to aDwight-Lloyd type sintering machine and charged on a palette.Thereafter, the sintering was performed on the palette followed bymeasurements of ore composition and the reducibility. Measurements ofones according to the inventive method and the conventional method areshown in Table 3. The measurement was performed of the sintered oreobtained by Dwight-Lloyd type sintering machine having a productioncapacity of 9300 tons/day.

As shown in Table 3, when the granulation method according to theinvention is adopted, as to the ore composition, hematite (He) high inthe reducibility increased, calcium silicate (CS) low in thereducibility decreased, and, as shown in FIG. 13, fine pores due tohematite (He) increased; accordingly, the reducibility increased by 5%in comparison with one according to the conventional method.

Furthermore, pseudo particles manufactured according to the granulationmethod (method B) of the invention were similarly supplied toDwight-Lloyd type sintering machine followed by sintering. Results weresimilar to the above.

Still furthermore, results of EPMA measurement of cross sections ofsintered bodies of the pseudo particles according to the inventivemethod and conventional method are shown in FIG. 14. FIG. 14 is obtainedby tracing an EPMA photograph, and with a Ca portion blacked out andwith a Fe portion outlined, a dispersion state of Ca is made seeablewith ease. While in the conventional one, Ca (black portion) distributesuniversally, in the inventive one, Ca is found only in the exteriorcoating portion. Accordingly, it is confirmed that owing to theapplication of the exterior coating of limestone according to theinventive method, hematite remains inside of the sintered ore, and inthe surroundings thereof calcium ferrite is generated. That is, it isconfirmed that a sintered structure such as shown in FIG. 4 in which onthe surface of the sintered ore calcium ferrite (CF) high in thestrength is generated and toward the inside portion of the sintered orehematite (He) high in the reducibility is selectively generated could beobtained.

Furthermore, pseudo particles manufactured according to the granulationmethod (method C) of the invention were similarly supplied toDwight-Lloyd type sintering machine followed by sintering. Results ofthe sintering and EPMA measurements were similar to the above.

FIG. 15 shows results of measurements of the reducibility (JIS-RI),yield, and productivity. According to the inventive method, incomparison with one according to the conventional method, thereducibility JIS-RI is increased by substantially 5%, the yield isimproved by 0.5% and the productivity is improved by substantially 18%.

Embodiment 2

With the apparatus shown in FIG. 21, projection experiment of theadditional coating auxiliary raw material was performed. The apparatusshown in FIG. 21 is equipped with driving pulley 12 at one end andfreely rotatable pulley 13 at the other end, and around outerperipheries of the driving pulley 12 and the pulley 13, endless belt 14is wound. To the driving pulley 12, driving motor 33 that rotationallydrives the driving pulley 12 is connected, the belt 14 being made tooperate owing to the rotational drive of the driving pulley 12. To thedriving motor 33, speed control means 34 for controlling the speed ofthe belt 14 of the additional coating conveyer is connected, and therebyan initial projection speed of the additional coating auxiliary rawmaterial 8 can be controlled. A drop distance from a center of thedriving pulley 12 to the ground is 1750 mm (1.75 m), a distance betweenthe driving pulley 12 and the pulley 13 being 10000 mm (10 m).

In the projection experiment, projections were performed with the speedof the belt 14 set at 4 levels of 60 m/min, 180 m/min, 240 m/min and 300m/min, and with the projection elevation angle of the additional coatingauxiliary raw material 8 set at 0 degree, and projection distances froma central axis line of the driving pulley 12 to a position where theadditional coating auxiliary raw material 8 reached the ground weremeasured.

Furthermore, when the additional coating auxiliary raw material 8 isprojected, theoretical calculation values of a projection distance fromthe central axis line of the driving pulley 12 to a place where theadditional coating auxiliary raw material 8 reaches the ground and adrop distance from a center of the driving pulley 12 to the ground canbe expressed by the following (1) and (2) equations when calculatedwithout considering the air resistance.Projection distance=V×cos θ×t   (1)Drop distance=V×sin θ×t−g×t ²/2   (2)

In the above equations, θ, V, and t, respectively, denote a projectionelevation angle, a speed of the belt, and time. g denotes gravitationalacceleration.

Then, measurements and calculated values of the projection distance werecompared. Results thereof are shown in FIG. 22. In FIG. 22, whencalculating the calculated values of the drop distance and projectiondistance, the projection elevation angle θ was set at 0 degree.

With reference to FIG. 22, it is found that measurements (main streamrange) and calculated values of the projection distance when the dropdistance is set at 1.75 m overlap each other for all of 4 levels of beltspeed of 60 m/min, 180 m/min, 240 m/min, and 300 m/min.

Accordingly, in the manufacturing apparatus 1 of the sintering materialshown in FIGS. 16 through 20, a predetermined position on the exhaustoutlet side in the drum mixer 4 wherein the exhaust end D of theadditional coating conveyer 10 is located and a speed of the belt 14 ofthe additional coating conveyer 10 can be adjusted based on the aboveequations (1) and (2).

Embodiment 3

Furthermore, with the apparatus shown in FIG. 21, the additional coatingauxiliary raw material 8 of transfer amount of 8 kg/s (coke: 3 kg/s andlimestone: 5 kg/s) was projected at a speed of the belt 14 of 300 m/sand a projection elevation angle of 0 degree, and the dispersibility wasinvestigated. Results are shown in FIG. 23.

With reference to FIG. 23, it can be understood that in the neighborhoodof the projection distance of 3000 mm (3 m), within a width of 300 mm,more than 90% of weight exists. Accordingly, in the manufacturingapparatus 1 of the sintering material shown in FIGS. 16 through 20, theadditional coating auxiliary raw material 8 projected from theadditional coating conveyer 10 can be additionally coated without beingunnecessarily dispersed in the projection position. Accordingly, themanufacturing apparatus 1 can be sufficiently utilized as apparatus thatadds a limestone base powdery material and a solid fuel type powderymaterial that is a heat source in a exterior coating region disposed inthe middle on a downstream side until pseudo particles of material foruse in sintering reaches the exhaust outlet of the drum mixer.

INDUSTRIAL APPLICABILITY

As mentioned above, according to the manufacturing method of thesintering material of the invention, when the limestone base powderymaterial and solid fuel type powdery material that is a heat source areadded in the exterior coating region disposed in the middle on adownstream side until pseudo particles reach the exhaust outlet of thedrum mixer, a pseudo particle material for use in sintering in which thelimestone base powdery material and solid fuel type powdery materialthat is a heat source are deposited and formed on the exterior coatingportion of the pseudo particles can be manufactured. Accordingly, in thecourse of sintering with Dwight-Lloyd type sintering machine, calciumsilicate (CS) low in the cold strength is suppressed from generating,calcium ferrite (CF) high in the strength is formed on the surface ofthe sintered ore, and hematite (He) high in the reducibility isselectively formed toward the inside of the sintered ore. As a result,the sintered ore rich in the fine pores, excellent in the reducibilityand high in the cold strength can be manufactured with highproductivity.

Other than the above, manufacturing apparatus of the sintering materialsuitable for the sintered ore that is simple, economical and easy in themaintenance of the apparatus can be provided.

TABLE 1 Hematite Calcium ferrite Calcium silicate Magnetite (He) (CF)(CS) (Mg) Reducibility 50 34 3 27 (%) Tensile 49 102 19 58 strength(MPa)

TABLE 2 Compounding Brand ratio (%) Particle size (mm) Iron ore (coarseparticle) 82 3.0 SiO₂-containing material 3 1.0 (fine particle)Limestone base powdery material 10 1.5 Coke powder 5 0.8

TABLE 3 Measurements Ore composition (% by mass) Calcium Calcium Reduci-Granulation Hematite ferrite silicate Magnetite bility method (He) (CF)(CS) (Mg) (%) Inventive method 51.2 27.3 11.3 10.2 70 (exterior coatingtime: 60 s) Conventional 42.0 33.9 13.2 10.9 65 method

1. A manufacturing method of a material for use in sinteringcharacterized in that, as a pretreatment of a manufacturing process of asintered ore for use in a blast furnace with a Dwight-Lloyd typesintering machine of downward suction, when a sintering materialincluding iron ore, a SiO₂-containing material, a limestone base powderymaterial and a solid fuel type powdery material is granulated by use ofa drum mixer, the method comprises: charging sintering material,excepting the limestone base powdery material and solid fuel typepowdery material, to a charge inlet of the drum mixer, granulating thesintering material in the drum mixer, and charging an additional coatingauxiliary raw material to the drum mixer in a region disposed in adownstream side of the drum mixer and at a location where a staying timeduring which the sintering material reaches up to an exhaust outlet ofthe drum mixer is in the range of from 10 to 90 seconds, and therebyuntil reaching the exhaust outlet, the additional coating auxiliary rawmaterial is deposited and formed on a exterior coating portion of thegranulated sintering material.
 2. The manufacturing method of a materialfor use in sintering as set forth in claim 1 characterized in that theadditional coating auxiliary raw material is the limestone base powderymaterial and the solid fuel type powdery material.
 3. The manufacturingmethod of a material for use in sintering as set forth in claim 2characterized in that the limestone base powdery material is charged tothe drum mixer, and the solid fuel type powdery material is charged tothe drum mixer, and thereby until reaching the exhaust outlet thelimestone base powdery material and the solid fuel type powdery materialare deposited and formed, successively, on the exterior coating portionof the sintering material.
 4. The manufacturing method of a material foruse in sintering as set forth in claim 1 characterized in that the drummixer is divided into a plurality of drum mixers, and a final drum mixeris set at a drum mixer length in which a staying time reaching from thecharge inlet up to the exhaust outlet is set in the range of from 10 to90 seconds.
 5. The manufacturing method of a material for use insintering as set forth in claim 4 characterized in that the additionalcoating auxiliary raw material is added in a region disposed in adownstream side where a staying time during which the sintering materialreaches an exhaust outlet of the final drum mixer is in the range offrom 10 to 90 seconds, and thereby until reaching the exhaust outlet,the additional coating auxiliary raw material is deposited and formed onthe exterior coating portion of the sintering material.
 6. Amanufacturing apparatus of a sintering material characterized in that ina manufacturing apparatus including a drum mixer by which a sinteringmaterial is, while rolling and transferring, formed into pseudoparticles; and an additional coating conveyer that projects anadditional coating auxiliary raw material into the drum mixer afterforming pseudo particles of the sintering material, on an exhaust outletside of the drum mixer, wherein an additional coating conveyer and itsexhaust end are positioned outside of the drum mixer so that the exhaustend thereof faces the exhaust outlet of the drum mixer.
 7. Themanufacturing apparatus of a sintering material as set forth in claim 6characterized in that the additional coating conveyer is capable ofcontrolling one or both of an initial speed and/or an elevation angle ofthe additional coating auxiliary raw material with which the additionalcoating auxiliary raw material for additional coating is projected intothe drum mixer.
 8. The manufacturing apparatus of a sintering materialas set forth in claim 6 characterized in that it further includesmovement means for moving the additional coating conveyer so that theexhaust end of the additional coating conveyer moves between apredetermined position on an exhaust outlet side inside of the drummixer and an outside position of the exhaust outlet of the drum mixer.9. The manufacturing apparatus of a sintering material as set forth inclaim 6 characterized in that it further includes speed control meansfor controlling a belt speed of the additional coating conveyer, therebycontrolling an initial projection speed of the additional coatingauxiliary raw material that is projected into the drum mixer.
 10. Themanufacturing apparatus of a sintering material as set forth in claim 9characterized in that the exhaust end of the additional coating conveyeris positioned on the exhaust outlet side inside of the drum mixer, andthe belt speed of the additional coating conveyer is controlled so thata projection position of the additional coating auxiliary raw materialis in a region disposed in a downstream side where a staying time duringwhich the sintering material reaches the exhaust outlet of the drummixer is in the range of from 10 to 90 seconds.
 11. The manufacturingmethod of a material for use in sintering as set forth in claim 2characterized in that the drum mixer is divided into a plurality of drummixers, and a final drum mixer is set at a drum mixer length in which astaying time reaching from the charge inlet up to the exhaust outlet isset in the range of from 10 to 90 seconds.
 12. The manufacturing methodof a material for use in sintering as set forth in claim 3 characterizedin that the drum mixer is divided into a plurality of drum mixers, and afinal drum mixer is set at a drum mixer length in which a staying timereaching from the charge inlet up to the exhaust outlet is set in therange of from 10 to 90 seconds.
 13. The manufacturing method of amaterial for use in sintering as set forth in claim 2 characterized inthat the drum mixer is divided into a plurality of drum mixers, and theadditional coating auxiliary raw material is added in a region disposedin a downstream side where a staying time during which the sinteringmaterial reaches an exhaust outlet of the final drum mixer is in therange of from 10 to 90 seconds, and thereby until reaching the exhaustoutlet, the additional coating auxiliary raw material is deposited andformed on the exterior coating portion of the sintering material. 14.The manufacturing method of a material for use in sintering as set forthin claim 3 characterized in that the drum mixer is divided into aplurality of drum mixers, and the additional coating auxiliary rawmaterial is added in a region disposed in a downstream side where astaying time during which the sintering material reaches an exhaustoutlet of the final drum mixer is in the range of from 10 to 90 seconds,and thereby until reaching the exhaust outlet, the additional coatingauxiliary raw material is deposited and formed on the exterior coatingportion of the sintering material.
 15. The manufacturing apparatus of asintering material as set forth in claim 7 characterized in that itfurther includes movement means for moving the additional coatingconveyer so that the exhaust end of the additional coating conveyermoves between a predetermined position on an exhaust outlet side insideof the drum mixer and an outside position of the exhaust outlet of thedrum mixer.
 16. The manufacturing apparatus of a sintering material asset forth in claim 7 characterized in that it further includes speedcontrol means for controlling a belt speed of the additional coatingconveyer, thereby controlling an initial projection speed of theadditional coating auxiliary raw material that is projected into thedrum mixer.
 17. The manufacturing apparatus of a sintering material asset forth in claim 8 characterized in that it further includes speedcontrol means for controlling a belt speed of the additional coatingconveyer, thereby controlling an initial projection speed of theadditional coating auxiliary raw material that is projected into thedrum mixer.